The present invention relates to a substrate processing apparatus for automatically processing a large number of flat substrates in a sequential order in a vacuum atmosphere.
In thin film formation in the silicon monolithic IC fabrication process, about 1-.mu.m thick thin metal or insulating film is formed on each of a large number of silicon wafers having, e.g., a diameter of 125 mm and a thickness of about 0.5 mm. The electrical, mechanical and physical characteristics of thin films formed are generally good when an impurity gas partial pressure in a vacuum chamber is low. From this reason, the vacuum chamber for sputtering is preferably exposed in an outer atmosphere only for a minimum period of time. In order to process a large number of silicon wafers, it is preferable to shorten gas supply/exhaust time and evacuation time with respect to the total processing time. In order to effectively perform reproducible thin film formation for a large number of wafers, the wafers are preferably automatically fed without being manually handled by the operator. Furthermore, a thin film of only a desired material and uniform thickness must be formed on the wafer. Neither dust particles should be mixed in nor the film should be partially formed to cause a pinhole. The wafers are vertically held during deposition so as to prevent dust particles from being accumulated on the wafers even if dust particles are generated in the vacuum chamber.
Various types of sputtering apparatuses have been proposed. U.S. Pat. No. 4,405,435 describes sputtering apparatuses of the related art. In such a sputtering apparatus, the wafers are horizontally fed by a belt conveyor mechanism one by one and heated or preprocessed, e.g., sputter etched. The preprocessed wafer is fed into a sputtering chamber. Horizontal and vertical position control of the wafer is performed by an arm holder mechanism. According to this mechanism, reliability of transfer operation between the belt conveyor mechanism for the wafer and an arm serving as a wafer holder during film deposition is so poor that the wafer cannot be properly held. The next unprocessed wafer must wait until the current unprocessed wafer is held by the arm holder mechanism, thus resulting in one of the obstacles preventing high productivity.
In the film deposition chamber, the horizontally or vertically movable arm is combined with a single cathode. The resultant mechanism can perform only deposition of a single material in a single film deposition chamber. In order to deposit two different films on a single wafer according to the conventional system, another horizontally or vertically movable mechanism consisting of an arm and a cathode is required to feed the wafer again, thus requiring a large and complex system.